From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f174.google.com ([209.85.213.174]:36866 "EHLO mail-ig0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755383AbaIWNiN (ORCPT ); Tue, 23 Sep 2014 09:38:13 -0400 Received: by mail-ig0-f174.google.com with SMTP id r10so4576181igi.7 for ; Tue, 23 Sep 2014 06:38:12 -0700 (PDT) Message-ID: <542177BF.2000808@gmail.com> Date: Tue, 23 Sep 2014 09:38:07 -0400 From: Austin S Hemmelgarn MIME-Version: 1.0 To: lists@xunil.at, linux-btrfs@vger.kernel.org Subject: Re: general thoughts and questions + general and RAID5/6 stability? References: <8D1A2626CC69D79-11FC-A2C3@webmail-va141.sysops.aol.com> <54208BBC.1000700@xunil.at> <542162A8.2010700@gmail.com> <5421706F.6070301@xunil.at> In-Reply-To: <5421706F.6070301@xunil.at> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms080503030502010106040804" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms080503030502010106040804 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2014-09-23 09:06, Stefan G. Weichinger wrote: > Am 23.09.2014 um 14:08 schrieb Austin S Hemmelgarn: >> On 2014-09-22 16:51, Stefan G. Weichinger wrote: >>> Is re-creating btrfs-filesystems *recommended* in any way? >>> >>> Does that actually make a difference in the fs-structure? >>> >> I would recommend it, there are some newer features that you can only >> set at mkfs time. Quite often, when a new feature is implemented, it = is >> some time before things are such that it can be enabled online, and ev= en >> then that doesn't convert anything until it is rewritten. > > What features for example? Well, running 'mkfs.btrfs -O list-all' with 3.16 btrfs-progs gives the=20 following list of features: mixed-bg - mixed data and metadata block groups extref - increased hard-link limit per file to 65536 raid56 - raid56 extended format skinny-metadata - reduced size metadata extent refs no-holes - no explicit hole extents for files mixed-bg is something that you generally wouldn't want to change after mk= fs. extref can be enabled online, and the filesystem metadata gets updated=20 as-needed, and dosen't provide any real performance improvement (but is=20 needed for some mail servers that have HUGE mail-queues) I don't know anything about the raid56 option, but there isn't any way=20 to change it after mkfs. skinyy-metadata can be changed online, and the format gets updated on=20 rewrite of each metadata block. This one does provide a performance=20 improvement (stat() in particular runs noticeably faster). You should=20 probably enable this if it isn't already enabled, even if you don't=20 recreate your filesystem. no-holes cannot currently be changed online, and is a very recent=20 addition (post v3.14 btrfs-progs I believe) that provides improved=20 performance for sparse files (which is particularly useful if you are=20 doing things with fixed size virtual machine disk images). It's this last one that prompted me personally to recreate my=20 filesystems most recently, as I use sparse files to save space as much=20 as possible. > > I created my main btrfs a few months ago and would like to avoid > recreating it as this would mean restoring my root-fs on my main > workstation. > > Although I would do it if it is "worth it" ;-) > > I assume I could read some kind of version number out of the superblock= > or so? > > btrfs-show-super ? > AFAIK there isn't really any 'version number' that has any meaning in=20 the superblock (except for telling the kernel that it uses the stable=20 disk layout), however, there are flag bits that you can look for=20 (compat_flags, compat_ro_flags, and incompat_flags). I'm not 100%=20 certain what each bit means, but on my system with a only 1 month old=20 BTRFS filesystem, with extref, skinny-metadata, and no-holes turned on,=20 i have compat_flags: 0x0, compat_ro_flags: 0x0, and incompat_flags: 0x16b= =2E The other potentially significant thing is that the default=20 nodesize/leafsize has changed recently from 4096 to 16384, as that gives = somewhat better performance for most use cases. --------------ms080503030502010106040804 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIFuDCC BbQwggOcoAMCAQICAw9gVDANBgkqhkiG9w0BAQ0FADB5MRAwDgYDVQQKEwdSb290IENBMR4w HAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBIENlcnQgU2lnbmlu ZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2FjZXJ0Lm9yZzAeFw0xNDA4 MDgxMTMwNDRaFw0xNTAyMDQxMTMwNDRaMGMxGDAWBgNVBAMTD0NBY2VydCBXb1QgVXNlcjEj MCEGCSqGSIb3DQEJARYUYWhmZXJyb2luN0BnbWFpbC5jb20xIjAgBgkqhkiG9w0BCQEWE2Fo ZW1tZWxnQG9oaW9ndC5jb20wggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDdmm8R BM5D6fGiB6rpogPZbLYu6CkU6834rcJepfmxKnLarYUYM593/VGygfaaHAyuc8qLaRA3u1M0 Qp29flqmhv1VDTBZ+zFu6JgHjTDniBii1KOZRo0qV3jC5NvaS8KUM67+eQBjm29LhBWVi3+e a8jLxmogFXV0NGej+GHIr5zA9qKz2WJOEoGh0EfqZ2MQTmozcGI43/oqIYhRj8fRMkWXLUAF WsLzPQMpK19hD8fqwlxQWhBV8gsGRG54K5pyaQsjne7m89SF5M8JkNJPH39tHEvfv2Vhf7EM Y4WGyhLAULSlym1AI1uUHR1FfJaj3AChaEJZli/AdajYsqc7AgMBAAGjggFZMIIBVTAMBgNV HRMBAf8EAjAAMFYGCWCGSAGG+EIBDQRJFkdUbyBnZXQgeW91ciBvd24gY2VydGlmaWNhdGUg Zm9yIEZSRUUgaGVhZCBvdmVyIHRvIGh0dHA6Ly93d3cuQ0FjZXJ0Lm9yZzAOBgNVHQ8BAf8E BAMCA6gwQAYDVR0lBDkwNwYIKwYBBQUHAwQGCCsGAQUFBwMCBgorBgEEAYI3CgMEBgorBgEE AYI3CgMDBglghkgBhvhCBAEwMgYIKwYBBQUHAQEEJjAkMCIGCCsGAQUFBzABhhZodHRwOi8v b2NzcC5jYWNlcnQub3JnMDEGA1UdHwQqMCgwJqAkoCKGIGh0dHA6Ly9jcmwuY2FjZXJ0Lm9y Zy9yZXZva2UuY3JsMDQGA1UdEQQtMCuBFGFoZmVycm9pbjdAZ21haWwuY29tgRNhaGVtbWVs Z0BvaGlvZ3QuY29tMA0GCSqGSIb3DQEBDQUAA4ICAQCr4klxcZU/PDRBpUtlb+d6JXl2dfto OUP/6g19dpx6Ekt2pV1eujpIj5whh5KlCSPUgtHZI7BcksLSczQbxNDvRu6LNKqGJGvcp99k cWL1Z6BsgtvxWKkOmy1vB+2aPfDiQQiMCCLAqXwHiNDZhSkwmGsJ7KHMWgF/dRVDnsl6aOQZ jAcBMpUZxzA/bv4nY2PylVdqJWp9N7x86TF9sda1zRZiyUwy83eFTDNzefYPtc4MLppcaD4g Wt8U6T2ffQfCWVzDirhg4WmDH3MybDItjkSB2/+pgGOS4lgtEBMHzAGQqQ+5PojTHRyqu9Jc O59oIGrTaOtKV9nDeDtzNaQZgygJItJi9GoAl68AmIHxpS1rZUNV6X8ydFrEweFdRTVWhUEL 70Cnx84YBojXv01LYBSZaq18K8cERPLaIrUD2go+2ffjdE9ejvYDhNBllY+ufvRizIjQA1uC OdktVAN6auQob94kOOsWpoMSrzHHvOvVW/kbokmKzaLtcs9+nJoL+vPi2AyzbaoQASVZYOGW pE3daA0F5FJfcPZKCwd5wdnmT3dU1IRUxa5vMmgjP20lkfP8tCPtvZv2mmI2Nw5SaXNY4gVu WQrvkV2in+TnGqgEIwUrLVbx9G6PSYZZs07czhO+Q1iVuKdAwjL/AYK0Us9v50acIzbl5CWw ZGj3wjGCA6EwggOdAgEBMIGAMHkxEDAOBgNVBAoTB1Jvb3QgQ0ExHjAcBgNVBAsTFWh0dHA6 Ly93d3cuY2FjZXJ0Lm9yZzEiMCAGA1UEAxMZQ0EgQ2VydCBTaWduaW5nIEF1dGhvcml0eTEh MB8GCSqGSIb3DQEJARYSc3VwcG9ydEBjYWNlcnQub3JnAgMPYFQwCQYFKw4DAhoFAKCCAfUw GAYJKoZIhvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTQwOTIzMTMzODA3 WjAjBgkqhkiG9w0BCQQxFgQUNTCBFNymBtdN38E+30GC2iRNxAgwbAYJKoZIhvcNAQkPMV8w XTALBglghkgBZQMEASowCwYJYIZIAWUDBAECMAoGCCqGSIb3DQMHMA4GCCqGSIb3DQMCAgIA gDANBggqhkiG9w0DAgIBQDAHBgUrDgMCBzANBggqhkiG9w0DAgIBKDCBkQYJKwYBBAGCNxAE MYGDMIGAMHkxEDAOBgNVBAoTB1Jvb3QgQ0ExHjAcBgNVBAsTFWh0dHA6Ly93d3cuY2FjZXJ0 Lm9yZzEiMCAGA1UEAxMZQ0EgQ2VydCBTaWduaW5nIEF1dGhvcml0eTEhMB8GCSqGSIb3DQEJ ARYSc3VwcG9ydEBjYWNlcnQub3JnAgMPYFQwgZMGCyqGSIb3DQEJEAILMYGDoIGAMHkxEDAO BgNVBAoTB1Jvb3QgQ0ExHjAcBgNVBAsTFWh0dHA6Ly93d3cuY2FjZXJ0Lm9yZzEiMCAGA1UE AxMZQ0EgQ2VydCBTaWduaW5nIEF1dGhvcml0eTEhMB8GCSqGSIb3DQEJARYSc3VwcG9ydEBj YWNlcnQub3JnAgMPYFQwDQYJKoZIhvcNAQEBBQAEggEAfdxyEucM1PNwdPPJ0u0LXABB/cl5 vCDf821aYgje4MANlJQ9YpLFXlAHXWkxLCr1Vm35SigLgfRFbHfqMQxMREMWsYIFw7+dG4bV IPiDr5VLcZwFEHU+JWN1BlBpy6yQviXKUIbdouNwWeeCDC0jChCwWDBsvTuN5sEvDMuEXMjW pq6GRwT3tjDw1bBDQH9nSKaifXoPX/9Q/X25WMlp0gE0qjNN1v7sCC3AvvVB8KSZCP7xVEUt 964eUgmFgVdbs4pkQutLX9JZvwcl0gzKSz5IsT6PKbxR0nmj6sIW/rD5o9WjsyATPdQzqWtL H/LsNyxxGOVkpxctX3VAgtXQgAAAAAAAAA== --------------ms080503030502010106040804--